Don't consider /photos/list.json part of the base URL
HTML-escape photo descriptions

It's a pity that we'll lose links and such in Flickr photo
description links, but that's better than having XSS issues :-(
Update README to add the Trovebox support
Add Trovebox mock API server example images locally
Make returned photo info objects more generic

Now maps representing the info for a given photo always have the
same keys: :id, :title, :description, :page-url and :thumbnail-url.
Add unit tests for Trovebox